The
scope of inquiry related to endocrine disruption has broadened dramatically
over the past two decades of research.

Originally
framed only as "estrogen mimicry" or "estrogens in the environment,"
research has expanded to include many other hormone systems: estrogen
blocking as well as mimickry, androgen blocking, concern for interference
with thyroid hormones and progesterone, retinoids... the whole gamut.

As
research continues to mount about the range of chemical-signalling
systems vulnerable to disruption, it is becoming apparent that endocrine
disruption is most likely but one example of a broader class of
contamination effects, termed "signal disruption."

New
results are being published frequently in the scientific literature
that continue to broaden the scope of inquiry.

Even
for single contaminants working through "traditional" endpoints
like estrogen mimickry, the science has become more complex and more
challenging to standard approaches to chemical regulation. It turns
out that endocrine disrupting
chemicals violate a basic assumption of toxicology and modern risk
assessment. For classic toxicants, "the dose makes
the poison." Higher doses lead to higher effects.
For some endocrine disrupting chemicals, however, effects may disappear
at higher levels, or become different qualitatively. New research
is illuminating the mechanisms by which these not-so-unusual patterns
occur.